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Thursday, July 29, 2010

Discrete Landau Levels In Graphene

Graphene ordinarily has continuous energy levels. However, as was recently shown that by adding strain, one can easily produce discrete landau levels. This achieved the equivalent of a 300 tesla magnetic field which is 10 times larger than any steady state magnetic field ever produce in a laboratory. This pivotal research paves the way to a future in which graphene will be used in optoelectronics.

Strain-Induced Pseudo–Magnetic Fields Greater Than 300 Tesla in Graphene Nanobubbles
N. Levy,1,2,*, S. A. Burke,1,*, K. L. Meaker,1 M. Panlasigui,1 A. Zettl,1,2 F. Guinea,3 A. H. Castro Neto,4 M. F. Crommie1,2,

Recent theoretical proposals suggest that strain can be used to engineer graphene electronic states through the creation of a pseudo–magnetic field. This effect is unique to graphene because of its massless Dirac fermion-like band structure and particular lattice symmetry (C3v). Here, we present experimental spectroscopic measurements by scanning tunneling microscopy of highly strained nanobubbles that form when graphene is grown on a platinum (111) surface. The nanobubbles exhibit Landau levels that form in the presence of strain-induced pseudo–magnetic fields greater than 300 tesla. This demonstration of enormous pseudo–magnetic fields opens the door to both the study of charge carriers in previously inaccessible high magnetic field regimes and deliberate mechanical control over electronic structure in graphene or so-called "strain engineering."

1 Department of Physics, University of California Berkeley, Berkeley, CA 94720, USA.
2 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
3 Instituto de Ciencia de Materiales de Madrid (CSIC), Madrid 28049, Spain.
4 Department of Physics, Boston University, Boston, MA 02215, USA.
* These authors contributed equally to this work.

Present address: Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.

Present address: Department of Physics and Astronomy and Department of Chemistry, University of British Columbia, Vancouver, BC V6T 121, Canada.

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